That cage is much too small for gerbils (also it seems to be only the topper). The absolute minimum people suggest is a 20 gallon (and personally I would say that should be a 20 gallon long and only with a topper unless for elderly and less active gerbils), but you should aim for 40 gallons or bigger.
They do best in pairs, and ideally only a pair (not a larger group). Groups come with a much higher risk of declanning. We're actually collecting some data on clan sizes and outcomes over at The Gerbil Forum on declanning rates and so far our data includes:
- 18+ pairs with a 0% declan rate
- 5 trios with a 60% declan rate
- 3 larger groups with a 100% declan rate
So you can see that pairs are by far the safest way to keep gerbils. Obviously the risk of declan is not really 0% even with a pair (our sample size is just too small right now), but it's low.
They do need access to a sand bath, and you don't necessarily need two. Gerbils aren't like dwarf hamsters where you need two of everything, so one nesting box, one wheel, one water bottle, is all fine (but ideally have more than one water source just for backup in case one breaks or spills).
You'll read online that the minimum wheel size is 8 inches but I don't agree with that. I suggest 10 inches as a minimum but as big as possible really. They need Syrian-sized wheels because of their tails.
Gerbils can be difficult to handle when they are young but they tend to mellow with time. It's not necessarily that they're scared, they're just very fast and busy. They're usually very eager to engage with humans, but not necessarily in a way that involves being picked up. A great way to interact with gerbils is to transport them to an enclosed run and then sit in with them and let them climb all over you. They may also enjoy running up your arm to your shoulder and you can easily train most gerbils to hop onto your hand for a treat.
